The Daleks believe they can find the Time Machine using their seismic detector while orders are given for the extermination of the time travellers. Vicki & Ian flee from the beast in the tunnels. The Daleks encounter an Aridian,native to the planet and exterminate them. The Doctor & Barbara have met other Aridians who explains how the suns got closer (the planet was drawn closer to the suns?) drying up the oceans (well if you name your planet Aridus you're asking for something to happen to turn it into a desert) freeing the Mire Beasts from the slime they inhabited and unleashing them to pray on the other inhabitants where they multiplied at a huge rate. The Aridians believe the missing travellers are trapped in the tunnels that are about to be destroyed to keep the Mire Beasts from further invading the city. Vicki is grabbed by a Mire Beast as the detonation occurs causing Ian to be struck by falling rock and knocked out. The Aridians shelter the Doctor & Barbara from the Daleks. The Daleks find the Tardis and decide to take some Aridians prisoner to get them to dig out the Tardis. The Daleks issue an ultimatum: The Aridians will turn the travellers over or the city will be destroyed. The Doctor tries to leave but they are held prisoner. The excavation complete the Daleks execute their slave party. However attempts to destroy the Tardis fail, so the Daleks leave a guard on the Tardis. The Aridians agree to hand the Doctor over and Vicki is captured in the tunnels. As the travellers are about to be handed over a Mire Beast bursts into the city allowing them to escape. Ian has woken and found his way back to the Tardis but had to hide at which point he is reunited with his friends. Ian plots a distraction to aid their escape causing Barbara to loose another cardigan (as per the Space Museum) and the Doctor his coat. The Daleks are taken in by the diversion and move off to pursue, one of which is destroyed in a pit trap, allowing the Time Travellers to escape in the Tardis. The Dalek Supreme sends orders for the Daleks to pursue them.

That wasn't too bad at all. Decent episode that starts a bit slow, half way through I was questioning whether it would work without the Daleks as they didn't seem to be there much but as the episode went on they make their presence known. We've seen them taking slaves before in Dalek Invasion of Earth and they will again (Day, Planet, Death & Destiny) as it seems to be a common Dalek trait to get lesser life forms to do the hard work. The casual extermination of the workers at the end highlights their evil. There's several shots of the Daleks in the sand on location which highlights the difficulty working with these props outside the studio - in one shot it looks like the Dalek is being picked up and moved by the operator inside.

Making his television début in this episode as one of the Aridians is Hywel Bennet, later to find fame starring in the ITV sitcom Shelley.